Process for producing mahogany acids and mahogany soaps



Patented Dec. 26, 1950 UNITED: STATES PATENT oFF-lce raoosss FORPRODUCING MAHOGANY ACIDS AND MAHOGANY SOAPS Charles A. Cohen, RosellePark, N. J., assignor to Standard Oil Develo ration of Delaware I NoDra'wing.

pmcnt Company, a corpo Application December 3, 1946, Serial No. 713,843

6 Claims. (o1..2eo 504) This invention relates to an improved mahoganyacid soap and the process of its production.

The present application is a continuation in part of my copendingapplication x Serial No. 505,507 filed October 8, 1943, now Patent No.

2,413,311 dated December 31, 1946 which in turn is a continuation inpart of my earlier application Serial No. 371,777, filed December 26,1940, now Patent No. 2,388,677 dated January 13, 1946. This presentapplication also contains subject matter common with that in myapplication Serial No. 370,626 filed December 18, 1940 which becameabandoned on September 18, 1945.

In the production of highly refined mineral oils or white oils, by theaction of strong sulfuric acid or fuming sulfuric acid on a petroleumdistillate, two major by-products are formed. The

first consists of a group of oil-soluble, sulfonic acids which remain inthe oil layer after the acid sludge has been separated and is known asmahogany acid and the product of their neutralization with a base isknown as a mahogany soap. The color of mahogany soaps may vary ,fromwater-white to a deep red depending on their degree of purity.

The second major by-product consists of a 'group ofwater-soluble-sulfonic acids which remain in. the sludge layer and maybe separated by appropriate means. These are known as green or blackacids.

Heretofore, mahogany soaps have been secured by first drasticallytreating a petroleum oil fraction with strong sulfuric acid or fumingsulfuric acid, followed by separation of the acid sludge from the oil,neutralization of the acid oil or so called sour oil with an alkali,followed by substantially complete removal of the oil-soluble sulfonicacid salts or mahogany soaps from the oil by water-washing or by dilutealcohol or by other substantially immiscible solvent. The mahogany soapsare recovered from their solvent solution by removing the solvent bydistillation. If sulfonic acids per se are desired, they are extractedwithout neutralization of the oil.

The mahogany soaps secured by this means have normally been contaminatedin the past with impurities such as sodium or other metal hydroxide orcarbonate, etc., depending on the alkali used for neutralization,together with varying proportions of sodium sulfate and sodium sulfite.'Ihey may vary in color from a straw through mahogany to a deep red.Although normally considered a by-product of the manufacture of whiteoil, the mahogany soaps have considerable economic value, When properlypurifled they may be used as emulsifying agents in the preparation ofsoluble oils for use in textile wet finishing, cutting oils, fatliquoring of leathers, or may be used as fat-splitting agents, wettingagents, surface tension depressants and the like.

It has now been found that the major part of the colorof the mahoganysoaps as ordinarily prepared is due to the inclusion of pepper sludge?in the acid oil at the time the oil is neutralized and extracted withsolvent. As indicated above. the oil is treated with strong or fumingsulfuric acid and the sludge separated from the'oll by settling anddecantation. The acid oil leaving the settler contains some dissolvedsulfur dioxide, some mahogany sulfomc acids in solution and in addition,is nearly opaque and black in color due to the presence of a quantity ofsuspended or dispersed particles or globules of green or black acids,tar and acid sludge which shows no disposition to settle even, afterlong standing.- These dispersed particles of black acid, tar, sludge,and unreacted sulfuric acid, etc'., are known collectively as peppersludge and appear to be in a colloidal state of suspension. The termpepper sludge, as used herein, refers to' all these materials, and itishighly acidic in natureand when neutralized has great tinctorial power.When acid oil containing such pepper sludge is neutralized and extracted with a solvent, the neutralized pepper sludge is included inthe-mahogany soap giving the soap its characteristic color.- If thesulfonic acids are extracted without neutralization they are likewisecolored.

Pure mahogany sulfonic acids are strong acids and give neutral salts orsoaps with strong alkaas emulsifying agents for oils in regions wherehard water is available. On the other hand,, alkaline earth salts of thegreen or black acids, when added to. emulsions, cause a reversal inphase and are often used to break emulsions. The inclusion, therefore,of some pepper sludge with its attendant green acid in the mahogany soapat the time of neutralization, gives not only a poorer colored soap butalso causes a decrease in its emulsifying power.

One of the major objects of this invention is to prepare mahogany acidsand mahogany soaps entirely free of pepper sludge or green acids andtheir neutralization products.

According to the present invention, a sulfuric acid-treated oil, aftersubstantial removal of the sludge by settling or by'centrifuging butbefore neutralization, is treated with a finely divided substanceselected from the group comprising filter aids of diatomaceous origin,materials of siliceous origin, such as tripoli or finely ground silica,or activated carbon, and the finely divided substance-pepper sludgecomplex removed, and the mahogany acid or the product of itsneutralization with'a base removed from the oil by means of 'asubstantially immiscible "solvent, such as water, dilute alcohol oracetone, or the like. The solvent is then recovered bydistillation'leaving the acid or soap. This process yields a product"which varies in color from a light yellow to Waterwhite.

Materials of 'diatomaceous origin which are suitable for the practice ofthis invention are commercially available as filter aids such as the SFMCelites and "Filte Cels or Dica'lites. Either the natural dried andground earth may be used or it may be calcined with or without alkali ormay be acid-treated and calcined. Materials of siliceous origin such astripoli or finely ground silica such as is used for polishing agents andcommercially available as Snow Floss or Super Floss are suitable as isfinely ground -carborundum. Another class of materials suitable for thepractice of this invention are the finely ground carbons which may benatural, acid treated, or activated types. Other materials of likenature maybe used but the above are the preferred types. Various finelyground clays, such-as Attapulgus fines, may be used but materials suchas b-entonite are not considered de- :sirable.

ISolid materials of the character described above, particularly whenused in small quantities,

are not materially adsorbent or absorbent of the preferentially oilsoluble sulfonic acids but are effective to absorb, adsorb orotherwisecombine or form a complex with the pepper sludge to form acoprecipitate.

may vary widely.

The quantity of materials used Normally, less than 1% on a weight/volumebasis, e. g. grams per 100 ml., is adequate and as little as 0.02% hasbeen found effective where the sulfonic acid and pepper sludge contentsare low. On the other hand quantities of 3% have been used in practiceover extended periods and the use of as much as is feasible in somecases. Normally, however, a desirable range would be from 0.2% to 0.8%.

" "The proper use of these solid materials as sorb'ents orco-precipitating agents accomplishes the -following: The colors of therecovered oil and sulfonic acids are improved; contamination of themahogany acids with sulfuric acid or the neutralized mahogany sopas withinorganic sulfate is prevented since all of the free sulfuric acid inthe system is removed along with the pepper sludge; contamination of themahogany acid with S02 or the neutralized mahogany soap with inorganicsulfite may be prevented by permitting removal of the dissolved S02 bysimple air blowing or by vacuum stripping without degrading the mahoganyacid or the oil; all of the water soluble sulfonic acids, i. e. greenacids, are removed and substantially all of the preferentially oilsoluble sulfonic acids are left in solution.

The diatomaceous filter aid or tripoli or silica and the like is addedto the acid oil in an amount equal to from 1 to lbs. per thousandgallons of oil. The method of treating the oil with the above substancesmay be varied from either the direct addition of these materials to theoil in the form of dry powder or the materials may be previously admixedwith a portion of clear oil to form a slurry which can be pumped intothe main body of the oil. The oil, after the addition of the filter aid,may be agitated for a period of from 5 minutes to hour. If, for example,filter aid has been used, the filter aid-pepper sludge complex is thenremoved either by filtering or by settling.

1f filtering alone is used, it may be done with conventional filterpresses such as the plate and frame press or with a continuous rotarytype of press. It is advantageous when using a filter press to precoatthe press with filter aid in the proportion of 5 to 10 pounds of filteraidfor every one-hundred square feet of filter press area. If settlingis the means used .ior removing the filter aid-pepper sludge complexfrom the acid oil, it may be accomplished by running the acid 'oilfilteraid mixture into a settling drum at a rate designed to give the oil asettling time of from 5 minutes to one hour. A combination of settlingand filtration may be used in that the oil after treatment is given asettling sufficient to drop most of the filter aid-pepper sludge complexout and is then finished'by filtering 'eitherwith or without theaddition of more filter aid. Analt'erhate method of separating thefilter aid sludge complex from the oil is by means of a centrifuge sucharea basket type or one capable of discharging a slurry continuously.

The inventor hasnot attempted to postulate a theoretical mechanism forthe operation of this invention but the diversity of materials"which aresuitable for the practice of this invention and the rapiditywith'wliic'h agglutination or clumping of the pepper sludge particlestakes place after the filter aid'or tripoli or silica has beenadded,"without diminishing within practical limits the originalmahogany'acid content'of the acid oil, has led the inventor to .believethat the phenomenon represents a mutual coprecipitation of oppositelycharged colloidal particles. A curious observation in the practice ofthis invention is that within certain limits, the less filter aid isused, the more rapidly does the filter aid-pepper sludge complex settle.This is thought to be due to the fact that the pepper sludge has arelatively high den sity and when precipitated with the filter aid, theless the amount of filter aid used the higher the resultant density. Ifthe .oil has been treated with enough acid to make a white oil, that is,

' shows no residual sulfonatable material, the oil leaving the settleror filter press is perfectly clear and water-white and has a color 'of30 Saybolt.

The oil leaving the sludge separator, where most of the sludge has beenpermitted to settle out, will vary in temperature from substantiallyoil-sludge'mixture in order to maintain a state of fluidity or 'toreduce the viscosity of the oil while settling.

The acid oil after contacting with filter aid, or silica or tripoli and.the like, andsettling or filtration, is perfectly free of pepper sludgeand contains the original amount of mahogany acids present along with acertain amount of dissolved sulfur dioxide. The oil may be neutralizedat this stage with a basic material such as the alkali hydroxides,carbonates and the like, or organic bases, such as triethanolamine,isopropanolamine and pentanolamine may be used. In order to save on theamount of alkaline material used or obviate the necessity of removinginorganic impurities such as sulfates, sul-fites, etc. from theneutralized mahogany soap in a later purification step, the sulfurdioxide may be removed by air blowing, or by countercurrent air or inertgas stripping in a packed or bubble plate column, or the acid oil may besubjected to vacuum at ordinary or elevated temperatures, by means wellknown to the art. The removal of the sulfur dioxide may be made aninherent feature of the filtration step, in that the filtration mayberun under vacuum such as is commonly done in the laboratory in a Buchnerfunnel or a combination of pressure and vacuum may be used.

In neutralizing the acid oil after removal of the sulfur dioxide, it isoften desirable for some purposes to add the stoichiometric quantity ofalkali. A solution of purifiedmahogany sulfonate in oil results, whichis usable without further treatment as a soluble oil in the textile andcutting oil trade, or the exactly neutralized soap may 2 be extractedwith an oil immiscible solvent.

Ordinarily, the mahogany soap is extracted from the oil afterneutralization, and the alkali may be dissolved in the immisciblesolvent at the time it is added to the acid oil. or the oil may be firstneutralized and then extracted with imm scible solvent. On settling, alower layer of solvent with dissolved soap settles out leaving a clearsupernatant oil. The washing step may be repeated as often as isrequired to remove all of the soap from the oil layer.

The solvent extracts are united and the solvents removed bydistillation, leaving as a residue the desired mahogany soaps. The soapsmay be further purified by solution in strong alcohol, or may beextracted with light naphtha while in dilute alcohol solution to removea small amount of oil which usually accompanies the soap.

The soaps made in accordance with this invention possess valuableadvantages over soaps of the prior art. In addition to showing a higherdegree of emulsifying power as compared to the same soap with attendantpepper-sludge, the new soap is free from staining tendencies when usedin the wet processing of white textiles.

The invention will be mor clearly illustrated by the following example:

Example 1 1000 gallons of an oil which when finished had a viscosity of85 seconds Saybolt at 100 F. was treated aft-er settling hours followingthe last acid dump with lbs. of J-M #545 Celite, agitated for a periodof 15 minutes at a temperature of about 35 0., allowed to settle foronehalf hour when most of the pepper sludge-filter aid complex hadsettled out, and then filtered through a plate and frame press which hadbeen previously precoated with the same filter aid to the extent of 5lbs; of' filter aid'for every hundred square feet of filter press area.The analysis of. the oil at this stage showed a sulfonic acid content ofapproximately 4 grams for every 100 cc. with a dissolved sulfur dioxidecontent equal to the -same quantity. The sulfur dioxide was re-- movedby vacuum stripping, the oil neutralized with a solution of sodiumcarbonate, and the mahogany soaps extracted from the oil with a 50%solution of isopropyl alcohol in water. 0n removal of the solvent, whichwas accomplished by distillation, a portion of the soap made up in a 10%by weight solution in a water-white oil gave the following colors in a 1cell in a Lovibond Tintometer: 1.2 yellow, .2 red. The same oil workedup for soap without the removal of the pepper sludge'by'means of filteraid gave a soap which had a color of 25 yellow, 4.1 red when made up tothe same concentration in a water-white oil. In testing both soaps foremulsibility, the

purified soap gave a good emulsion in 2 concentration whereas thunpurified soap required an 8% concentration for a similar emulsion.

It will be understood that the various treating steps and the conditionsunder which they are performed may be varied, as described in myaforesaid copending application Serial No. 505,507. Thus the sulfuricacid strength and volume, temperature of acid treatment and time ofcontact may be varied, depending on the viscosity of the oil used, thedegree and method of itsrefinement, other physical characteristics suchas specific gravity, aniline point, viscosity index, etc. Chemicalcharacteristics such as degree'of unsaturation, and percentagecomposition of paraffins, naphthenes and aromatics will also vary andrequire various conditions for ap propriate acid treatment. As indicatedabove.

the treatment temperatures may be from ambient temperature up to about100 C. or more, a suitable range being from 10 C. to 100 C. A range morecommonly used lies between 10 and C.

By the above process I have found it possible to produce oil solublesulphonates having a high degree of purity.

What is claimed is:

i. In the preparation of preferentially oilsoluble sulfonic acid soapsin which a hydrocarbon oil is treated with fuming sulfuric acid, thesludge separated, and the sour oil neutralized to form preferentiallyoil-soluble sulfonates, the

improvement comprising contacting the sour oil with from 0.02 to 10% ofa solid sorbent mate rial, removing the sorbent material, neutralizingthe oil. and recovering preferentially oil-soluble sulfonic acid soaps.

2. In the preparation of preferentially oil-j soluble sulfonic acidscans in which a hydrocarbon oil is treated with fuming sulfuric acid,the sludge separated, and the sour oil neutralized to formpreferentially oil-soluble sulfonates, the

improvement comprising contacting the sour oil with from 0.02 to 3% of asolid sorbent material,

removing the sorbent material, neutralizing the oil and recoveringpreferentially oil-soluble sulfonic acid soaps.

3. In the preparation of preferentially oilsoluble sulfonic acid soapsin which a hydrocarbon oil is treated with fuming sulfuric acid, thesludge separated, and the sour oil neutralized to form preferentiallyoil-soluble sulfonates, the improvement comprising contacting the souroil with from 0.02 to 0.8% of a solid sorbent material, removing thesorbent material, neutralizing the oil, and recovering. preferentiallyoil-soluble sultonic acidv soaps.

i; In the: preparation of preferentiallyoilsoiuble sulfonic acid:v soapsin. which. a: hydrocar-- b'on oil is treated with fuming sulfonic" acidthe sludge removed, the S02 separated and the. sour oil thenneutralized, the improvement which comprises treating the sour oil with0.02 to 3% of a solid sorbent material at a temperature within the rangeof from about 10 Cv to. about 100 6;, removing the solid sorbentmaterialirom the sour oil, neutralizing the sour oil to. convert thepreferentially oil-soluble sulfonic acids to the correspondingsulfonates and extracting the resulting preferentially oil-solublesulfonates from the neutralized oil.

5-. In the preparation of preferentially oilsoluble sulfonic acidsoapsin which a hydrocarhon: oil is treated with fuming sulfonic acid,the sludge removed, the S02 separated and the sour oil then neutralized,the improvement which comprises treating the sour oil with 0.02 to 3% ofa solid sorbent material at a temperature within the range of from about10 C. to about 100 (1., removing the solid sorbent material from thesour oil, extracting the preferentially oilsolublc sulfonic acids fromthe sour oil and neutralizing. the sulfonic acids to obtainpreferential'l-y oil-soluble sulfonates.

6. In the preparation of preferentially oil soluble sulfonic acids inwhich a hydrocarbon oil is treated with fuming sulfuric acid and thesludge separated from the sour oil, the improve ment comprisingcontacting the sour oil with from 0.02 to 10% of a solid sorbentmaterial,. re-

moving the sorbent'. material and. recovering preferentially oil solublesulfonic acids from the oil CHARLES A. com.

REFERENCES CITED The following references are of record. inthe file ofthis patent:

UNITED STATES PATENTS Number Name" Date 1,286,179- Humphreys: Nov. 26,19 18 1,387,868 Robinson. Aug.- 16,, 1921; 1,709,149 Phillips Apr. 16,1929 1,766,304 Petrofi ..d June 24, 1930 1,974,089 Tietis Sept. 18,.1935. 2,158,680 Retailliau May 16, 1930 2,179,008 Campbell -n w Nov. '1,1939 2,187,883 Lemmon Jan. 23, 1940 2,191,091.- Bray .l Feb. 20,. 19402,214,037 Archibald haw--. Sept. 10, 194.0 2,215,362 Robinsonluflnnm.Sept. 1'7, 1940 2,226Q092 Clarke Dec. 24, I940 2',2'2'7,'3'7=7- Mapesi ai-- Decl 3 1, 1940" 2,236,933 Bec Apr. 1, 19% 2,270,214 Adams: -l Jan.13, 1942 2,282,033 Chechot .-L- a-. May 5,1943- 2,340,947 Evans Feb. 8,194% 2,348,609 Cohen. May 9 1944 2,361,476 Higbee l Oct. 31,. 1944'2,361,805v Wilson. Oct. 31,. 19% 2,338,677- Cohen Nov..13,.19452,403,185 Lemmon c July 2,1945% 2,413,311- Cohen Dec.v 31, 1946

1. IN THE PREPARATION OF PREFERENTIALLY OILSOLUBLE SULFONIC ACID SOAPSIN WHICH A HYDROCARBON OIL IS TREATED WITH FUMING SULFURIC ACID, THESLUDGE SEPARATED, AND THE SOUR OIL NEUTRALIZED TO FORM PREFERENTIALLYOIL-SOLUBLE SULFONATES, THE IMPROVEMENT COMPRISING CONTACTING THE SOUROIL WITH FROM 0.02 TO 10% OF A SOLID SORBENT MATERIAL, REMOVING THESORBENT MATERIAL, NEUTRALIZING THE OIL AND RECOVERING PREFERENTIALLYOIL-SOLUBLE SULFONIC ACID SOAPS.